$def1 = "!defined(FLOAT_CODE)";
$def2 = "defined(FIXED_CODE)";

##</code><code>##

 
m/^(!defined|defined)\((.*?)\)$/;
print "$1----$2\n";

##</code><code>##

 
output case1: !defined----FLOAT_CODE 
output case2: defined----FIXED_CODE

##</code><code>##

m/^(\!|defined)(.*?)$/;
print "$1----$2\n";

##</code><code>##

output case1: !----defined(FLOAT_CODE)
output case2: defined----(FIXED_CODE)